1. Field of the Invention
This invention relates generally to golf club heads and more particularly to a novel construction for golf club heads comprising a lattice structure which is covered by a lightweight material to define the body of the golf club head.
2. Description of the Related Art
Golf club heads, specifically those that fall into the "woods" category, were originally manufactured from organic substances, hence the name "woods." The first "metal wood" golf club heads were made in 1870, gaining widespread use in the 1960's. These metal wood golf club heads were very durable and used primarily for practice range purposes. Metal wood heads were further developed and found wider acceptance for everyday use in the late 1970's. The club heads are typically made from a two-piece welded shell construction, and some manufacturers inject the assembled shells with a foam material to tune the noise generated by the collision of the club head with the golf ball and to adjust the head's final weight.
In an effort to make metal woods more playable for the average golfer, the total volume of the metal wood golf club head was increased in 1989. Although the widely practiced two-piece welded shell construction continued to be used, the method to cast the shells changed to a thin wall process. Regardless of the casting method used, the shell of the metal wood continues to be the load bearing structure. Because of the substantial increase in volume realized by this process, the metal wood club head became commonly known as an "oversized" club head and represents the present day state-of-the-art. The materials used in casting the oversized metal wood club head (hereafter "club head") have shifted from stainless steel to titanium, allowing for even larger club head sizes to be realized. The greater strength of titanium when compared to stainless steel allows for thinner club head wall thicknesses, resulting in larger and lighter weight club heads.
Although titanium two-piece welded shells can achieve larger volumes than stainless steel welded shells while maintaining the structural integrity of the load bearing shell, an additional benefit to titanium is that the material allows for a more functional use of discretionary weight. Discretionary weight is basically extra material which is added to a golf club head to adjust the club's hitting characteristics. This discretionary weight is added to the club head after the parameters for the club head have been set. These parameters consist of, but are not limited to, the desired size of the golf club head, wall thickness, structural integrity, and cosmetic considerations.
The performance of the club head can be engineered with different inertial properties resulting in different ball spins, ball speeds, and ball trajectories by the proper positioning of the discretionary weight. Moving the discretionary weight will alter the club head's center of gravity, thereby altering, among other things, the club's moment of inertia.
This ability to "tune" the club is why oversized metal woods perform better than conventional wood heads. Oversized metal woods allow the discretionary weight to be centralized further away from the impact point. Although placing the discretionary weight further from the point of impact translates into shorter distances for which the golf ball is driven after the golf club collides with the golf ball, increased stability of the golf club head is gained. This increase in stability yields better control, resulting in an increase in overall shot performance.
Currently, the size issue of oversized metal wood club head design has reached the point of diminishing returns. Within the current material limitations, the larger the club head, the less discretionary weight is available to tune the club head. Ideally, a new club head structure is needed that makes it possible to increase club head size and make available additional discretionary weight, thereby allowing further increases in golf club performance. The present invention is directed to a golf club head that satisfies this need for an improved structure which realizes the above benefits.